In 1970, H. B. Bartl et al. disclosed a very unique characteristic of a 12A7 crystal in which 2 oxygen atoms out of 66 oxygen atoms in a unit cell containing 2 molecules are clathrated in the form of “free oxygen” in space of cages present in the crystal (Non-Patent Document 1). Subsequently, it has also been disclosed that the free oxygen can be substituted with various types of anions.
Hosono, one of the inventors of the present invention, discovered that O2− at a concentration of approximately 1×1019 cm−3 is clathrated by measuring electron spin resonance of a C12A7 crystal that was synthesized by a solid phase reaction at 1,200° C. in air using CaCO3 and Al2O3 or Al(OH)3 as raw materials and has proposed a model in that part of the free oxygen ions, that are in the form of O2−, are present in the cages (Non-Patent Document 2).
The inventors of the present invention further discovered that when a raw material containing calcium and aluminum at an atomic equivalent ratio of approximately 12:14 is subjected to a solid phase reaction under controlled atmospheric and temperature conditions, a C12A7 compound can be obtained in which an active oxygen species at a high concentration of 1020 cm−3 or more is clathrated. Patent applications of the above compound itself, a manufacturing method thereof, means for extracting the clathrated ions, a method of identifying active oxygen ion radicals, and application of the compound were filed (Patent Document 1).
In addition, a method for clathrating and/or extracting active oxygen at approximately 700° C. by controlling an anion ion concentration of OH−1 or the like other than oxygen in the compound was further discovered, and a patent application thereof was also filed (Patent Document 2). Furthermore, it was also discovered that when an electric field is applied to a C12A7 compound containing active oxygen at a high concentration, high density O− ion beams can be obtained, and a patent application relating to this invention was also filed (Patent Document 3).
In addition, a C12A7 compound containing OH−1 ions at a concentration of 1021 cm−3 or more was synthesized by firing a powdered C12A7 compound in an oxygen atmosphere which was obtained by hydration reaction in water, a solvent containing H2O, or a gas containing a water vapor, and patent applications of the above compound itself, a manufacturing method thereof, a method for identifying OH− ions, and application of the compound were also filed (Patent Document 4).
In addition, it was also discovered that a C12A7 compound containing hydrogen anions is a material having high speed ion conductivity, and that the hydrogen anions can be extracted into vacuum by application of an electric field. Furthermore, the following were also discovered that green coloration occurs when UV or x-ray irradiation is performed and that an electrical insulator is permanently changed to an electrical conductor simultaneously with the above coloration and can again be returned to an insulating state by heating or intense visible light irradiation, and a patent application of the use of the above phenomena was also filed (Patent Document 5).
In addition, as a compound having a crystal structure identical with that of the C12A7 compound, a S12A7 compound has been known (Non-Patent Document 3). The inventors of the present invention also filed patent applications of a synthetic method of a S12A7 compound, a method for clathrating active oxygen ions, and application of the compound (Patent Document 6).
Furthermore, the inventors of the present invention also discovered that an electrical conductance of 10−6S/cm3 or more can be obtained when C12A7, S12A7, and a mixed crystal compound thereof clathrate an alkaline metal or ions, and a patent application of this discovery was also filed (Patent Document 7).
An electride compound is the concept that J. L. Dye first proposed (Non-Patent Document 4) and was first realized, for example, by a compound containing a crown ether as a cation and electrons as anions. The electride has been known as a material that exhibits electrical conductivity by hopping of electrons contained as anions. Subsequently, several organic electrides were discovered; however, these compounds are stable only at a low temperature, such as approximately 100 K or less, and are considerably unstable materials so as to react with air and/or water.
In recent years, an inorganic electride compound was discovered that was formed by doping cesium into a powdered zeolite compound containing silica as a skeleton thereof. In order to obtain stability at room temperature, this compound was prepared so as to enable silica zeolite to serve like a crown ether for forming a complex. However, this compound has also high reactivity with moisture and is chemically unstable (Non-Patent Document 5). In addition, a diode has also been proposed that uses superior electron emission properties of an electride compound (Patent Document 8); however, since the electride compounds that have been obtained as of today are unstable from thermal and chemical points of view, the proposed vacuum diode can only be operated at a low temperature.    Patent Document 1 Japanese Patent Application No. 2001-49524 (Japanese Unexamined Patent Application Publication No. 2002-3218)    Patent Document 2 Japanese Patent Application No. 2001-226843 (Japanese Unexamined Patent Application Publication No. 2003-40697)    Patent Document 3 Japanese Patent Application No. 2001-377293    Patent Document 4 Japanese Patent Application No. 2001-117546 (Japanese Unexamined Patent Application Publication No. 2002-316867)    Patent Document 5 Japanese Patent Application No. 2002-117314    Patent Document 6 Japanese Patent Application No. 2002-045302 (Japanese Unexamined Patent Application Publication No. 2003-238149)    Patent Document 7 Japanese Patent Application No. 2002-188561    Patent Document 8 U.S. Pat. No. 5,675,972 Specification and Drawings    Non-Patent Document 1 H. B. Bartl and T. Scheller, Neuses Jarhrb. Mineral, Monatsh. (1970), 547    Non-Patent Document 2 H. Hosono and Y. Abe, Inorg. Chem. 26, 1193, (1987), “Zairyo Kagaku (Material Science)”, vol. 33, No. 4, pp. 171 to 172, (1996)    Non-Patent Document 3 O. Yamaguchi et al., J. Am. Ceram. Soc. 69[2]C-36, (1986)    Non-Patent Document 4 F. J. Tehan, B. L. Barrett, J. L. Dye, J. Am. Chem. Soc., 96, 7203 to 7208 (1974)    Non-Patent Document 5 A. S. Ichimura, J. L. Dye, M. A. Camblor, L. A. Villaescusa, J. Am. Chem. Soc., 124, 1170, (2002)